local component=require("component")
local computer=require("computer")
local event=require("event")
local fs=require("filesystem")
local shell=require("shell")
local term=require("term")

local gpu=component.gpu

local byte,concat,floor=string.byte,table.concat,math.floor
local uptime=computer.uptime

local HEADER_SIZE=64
local MAX_SKIP=4
local RAM_SHARE=0.4
local REFILL=3
local KEY_SPACE,KEY_Q=32,113

local OP_BG,OP_FG,OP_BOTH,OP_TEXT=1,2,3,4



local function u16(s,o)return byte(s,o)*0x100+byte(s,o+1)end
local function u32(s,o)return u16(s,o)*0x10000+u16(s,o+2)end

local function fail(msg)
error(msg,0)
end




local function buildColorTable(header)
local rgb={}
for i=0,15 do
local o=17+i*3
rgb[i]=byte(header,o)*0x10000+byte(header,o+1)*0x100+byte(header,o+2)
end
for i=0,239 do
local r=floor(floor(i/40)*255/5+0.5)
local g=floor(floor(i/5)%8*255/7+0.5)
local b=floor(i%5*255/4+0.5)
rgb[16+i]=r*0x10000+g*0x100+b
end
return rgb
end




local function buildGlyphTable()
local chars={[0]=" ","▄","▀","█"}
local t={}
for n=1,4 do
t[n]={}
for b=0,255 do
local s={}
for i=1,n do
s[i]=chars[floor(b/4^(4-i))%4]
end
t[n][b]=concat(s)
end
end
return t
end



local function readIndex(dir)
local f,err=io.open(fs.concat(dir,"index.ocv"),"rb")
if not f then fail("cannot open index.ocv: "..tostring(err))end
local h=f:read(HEADER_SIZE)
f:close()
if not h or#h<HEADER_SIZE or h:sub(1,4)~="OCV5"then
fail("bad index.ocv (нужен OCV5, перекодируй через ocv_encode.py)")
end
local v={
dir=dir,
width=u16(h,5),
height=u16(h,7),
fps=u16(h,9)/100,
frames=u32(h,11),
parts=u16(h,15),
header=h,
}
if v.width<1 or v.height<1 or v.fps<=0 or v.frames<1 or v.parts<1 then
fail("bad index.ocv: пустое или повреждённое видео")
end
return v
end



local function openStream(video,capacity)
local part,file=0,nil
local queue,head,tail,bytes={},1,0,0
local eof=false
local stream={}

local function readFrame()
while true do
if not file then
part=part+1
if part>video.parts then return nil end
local path=fs.concat(video.dir,string.format("part%04d.ocv",part))
local err
file,err=io.open(path,"rb")
if not file then fail("cannot open "..path..": "..tostring(err))end
end
local head4=file:read(4)
if head4 and#head4==4 then
local len=u32(head4,1)
if len==0 then return""end
local data=file:read(len)
if not data or#data<len then fail("truncated frame in part "..part)end
return data
end
file:close()
file=nil
end
end

function stream.fill(maxFrames,yieldEvery)
local n=0
while not eof and bytes<capacity and n<maxFrames do
local data=readFrame()
if not data then eof=true;break end
tail=tail+1
queue[tail]=data
bytes=bytes+#data
n=n+1
if yieldEvery and n%yieldEvery==0 then event.pull(0)end
end
return n
end

function stream.next()
if head>tail then stream.fill(1)end
if head>tail then return nil end
local data=queue[head]
queue[head]=nil
head=head+1
bytes=bytes-#data
return data
end

function stream.buffered()return tail-head+1,bytes end

function stream.close()
if file then file:close();file=nil end
queue,head,tail,bytes={},1,0,0
end

return stream
end



local Display={}
Display.__index=Display

function Display.open(w,h,palette)
if gpu.maxDepth()<8 then fail("нужен GPU и экран Tier 3")end
local mw,mh=gpu.maxResolution()
if mw<w or mh<h then
fail(string.format("экран %dx%d меньше видео %dx%d",mw,mh,w,h))
end

local self=setmetatable({w=w,h=h},Display)
self.saved={
depth=gpu.getDepth(),
fg=gpu.getForeground(),
bg=gpu.getBackground(),
palette={},
}
self.saved.w,self.saved.h=gpu.getResolution()

gpu.setDepth(8)
gpu.setResolution(w,h)
for i=0,15 do self.saved.palette[i]=gpu.getPaletteColor(i)end
self:_applyPalette(palette)


if gpu.allocateBuffer then
local ok,buf=pcall(gpu.allocateBuffer,w,h)
if ok and buf then
self.buffer=buf
gpu.setActiveBuffer(buf)
self:_applyPalette(palette)
end
end

self:clear()
return self
end

function Display:_applyPalette(palette)
for i=0,15 do gpu.setPaletteColor(i,palette[i])end
end


function Display:clear()
gpu.setBackground(0x000000)
gpu.fill(1,1,self.w,self.h," ")
self:present()
end

function Display:present()
if self.buffer then
gpu.bitblt(0,1,1,self.w,self.h,self.buffer,1,1)
end
end

function Display:close()
local s=self.saved
pcall(function()
if self.buffer then
gpu.setActiveBuffer(0)
gpu.freeBuffer(self.buffer)
end
for i=0,15 do gpu.setPaletteColor(i,s.palette[i])end
gpu.setDepth(s.depth)
gpu.setResolution(s.w,s.h)
gpu.setForeground(s.fg)
gpu.setBackground(s.bg)
end)
term.clear()
end



local function makeRenderer(colors,glyphs)
local setBg,setFg,set=gpu.setBackground,gpu.setForeground,gpu.set
local g4=glyphs[4]
local parts={}

return function(data)
local p,n,sets=1,#data,0
while p<=n do
local op=byte(data,p)
if op==OP_TEXT then
local x,y,len=byte(data,p+1,p+3)
local q=p+4
if len<=4 then
set(x,y,glyphs[len][byte(data,q)])
p=q+1
sets=sets+1
else
local full=floor(len/4)
for i=1,full do parts[i]=g4[byte(data,q+i-1)]end
local cnt,rest=full,len-full*4
if rest>0 then
cnt=cnt+1
parts[cnt]=glyphs[rest][byte(data,q+full)]
end
set(x,y,concat(parts,"",1,cnt))
p=q+cnt
sets=sets+1
end
elseif op==OP_BOTH then
setBg(colors[byte(data,p+1)])
setFg(colors[byte(data,p+2)])
p=p+3
elseif op==OP_BG then
setBg(colors[byte(data,p+1)])
p=p+2
elseif op==OP_FG then
setFg(colors[byte(data,p+1)])
p=p+2
else
error(string.format("corrupted frame: op %d at %d",op,p),0)
end
end
return sets
end
end



local QUIT,PAUSE="quit","pause"

local function poll(timeout)
local name,_,char=event.pull(timeout)
if name=="interrupted"then return QUIT end
if name=="key_down"then
if char==KEY_Q then return QUIT end
if char==KEY_SPACE then return PAUSE end
end
end

local function waitUntil(deadline)
repeat
local cmd=poll(math.max(0,deadline-uptime()))
if cmd then return cmd end
until uptime()>=deadline
end



local function play(video,display,render,stats)
local capacity=math.max(64*1024,floor(computer.freeMemory()*RAM_SHARE))
local stream=openStream(video,capacity)
stream.fill(math.huge,8)
local frames0,bytes0=stream.buffered()
stats.preload=stats.preload or string.format("%d кадров / %d КБ",frames0,floor(bytes0/1024))

local interval=1/video.fps
local t0=uptime()
local skipped=0

local ok,result=pcall(function()
for k=0,video.frames-1 do
local data=stream.next()
if not data then return end

local c0=os.clock()
stats.sets=stats.sets+render(data)
stats.cpu=stats.cpu+(os.clock()-c0)
stats.drawn=stats.drawn+1

local due=t0+k*interval
local now=uptime()
local cmd

if display.buffer and now>due+interval and skipped<MAX_SKIP and k<video.frames-1 then

skipped=skipped+1
stats.late=stats.late+1
cmd=poll(0)
else
stream.fill(REFILL)
cmd=waitUntil(due)
display:present()
skipped=0
end

if cmd==PAUSE then
local p0=uptime()
repeat cmd=poll(math.huge)until cmd
t0=t0+(uptime()-p0)
end
if cmd==QUIT then return QUIT end
end
end)

stream.close()
if not ok then error(result,0)end
return result
end



local HEADROOM=0.7


local function recommend(stats,fps)
if stats.drawn==0 or stats.sets==0 then return end
local perSet=stats.cpu/stats.sets
local avgSets=stats.sets/stats.drawn
print(string.format("Не успевает: в среднем %d gpu.set на кадр, %.3f мс на вызов.",
floor(avgSets+0.5),perSet*1000))
local targets=fps>10 and{fps,10}or{fps}
local printed=false
for _,f in ipairs(targets)do
local budget=floor(HEADROOM/f/perSet/50)*50
if budget>=100 and budget<avgSets then
print(string.format("  перекодируй: --fps %g --max-sets %d",f,budget))
printed=true
end
end
if not printed then
if floor(HEADROOM/10/perSet)<100 then
print("  слишком медленно даже для 10 fps: уменьши --width/--height")
else
print("  рисование укладывается — тормозит не GPU, а диск или TPS сервера")
end
end
end



local function main(...)
local args,opts=shell.parse(...)
local dir=args[1]
if not dir then
print("usage: ocv <video_folder> [-l]")
print("  -l  зациклить   |   Space — пауза, Q / Ctrl+C — выход")
return
end
dir=shell.resolve(dir)
if not fs.isDirectory(dir)then fail("папка не найдена: "..dir)end

local video=readIndex(dir)
local colors=buildColorTable(video.header)
local render=makeRenderer(colors,buildGlyphTable())
local display=Display.open(video.width,video.height,colors)
local stats={drawn=0,late=0,cpu=0,sets=0}
local started=uptime()

local ok,err=pcall(function()
repeat
if play(video,display,render,stats)==QUIT then break end
if opts.l then display:clear()end
until not opts.l
end)

display:close()
if not ok and err~="interrupted"then fail(err)end

local elapsed=math.max(uptime()-started,1e-6)
print(string.format("%d кадров за %.1f с (%.1f fps), пропущено выводов: %d, CPU на кадр: %.1f мс",
stats.drawn,elapsed,(stats.drawn-stats.late)/elapsed,stats.late,
stats.cpu/math.max(stats.drawn,1)*1000))
print("Буфер ОЗУ при старте: "..tostring(stats.preload))
if stats.late>stats.drawn/10 then recommend(stats,video.fps)end
end

local ok,err=pcall(main,...)
if not ok then
io.stderr:write("ocv: "..tostring(err).."\n")
end